# 知几Kairos vs Luck日子

The clearest difference is in-app purchases: 知几Kairos at none against Luck日子's 3. Luck日子's advantage is update cadence (every 3 days vs fortnightly). On price, ads, device support and iOS requirement there is nothing between them.

Both are free to download. Luck日子 sells 3 in-app purchases, starting at $1.99 per month. 知几Kairos asks for nothing beyond the download.

知几Kairos ships an update fortnightly, Luck日子 every 3 days. The most recent releases landed on October 9, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | 知几Kairos | Luck日子 |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Fortnightly | **Every 3 days** |
| Size | 11 MB | 26 MB |
| Requires iOS | 17.0 | 17.0 |
| Devices | **iPhone, iPad** | iPhone |
| Age rating | 17+ | 4+ |
| Developer | [algormula Pte. Ltd.](https://appshunter.io/developer/1828508832) | [兵 李](https://appshunter.io/developer/1888184886) |

## What reviewers say

### 知几Kairos

[App page](https://appshunter.io/ios/app/kairos/id6758753321)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### Luck日子

[App page](https://appshunter.io/ios/app/luck/id6808837559)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| 择日月卡 | $1.99 | per month |
| 择日年卡 | $14.99 | per year |
| 择日 10 次卡 | $0.99 | one-time |


## Frequently asked questions

### Is 知几Kairos free?

知几Kairos is free to download, with no in-app purchases.

### Is Luck日子 free?

Luck日子 is free to download, with in-app purchases available.

### Do 知几Kairos or Luck日子 have ads?

Neither 知几Kairos nor Luck日子 shows ads.

### Which is updated more often, 知几Kairos or Luck日子?

知几Kairos ships an update fortnightly, and Luck日子 every 3 days. Most recently, 知几Kairos was updated on October 9, 2026 and Luck日子 on October 24, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*